1. Field of the Invention
The present invention relates to a substrate structure using a so-called carbon nano tube (CNT), a carbon nano fiber (CNF) or the like, which is a linear structure made of a carbon element and a manufacturing method of the same.
2. Description of the Related Art
A CNT and a CNF being linear structures of carbon-based self-organizing materials, in which, especially the CNT attracts attention because of its many appealing physical properties.
The CNT possesses a low electrical resistance and a high mechanical strength, and because of such excellent properties, it is expected to be applied to a wide range of fields such as a semiconductor device, various sensors such as an acceleration sensor, an electronic device and a heat radiating device, represented by an LSI.
In order to apply the CNT to a via portion of a wiring structure of the LSI, for example, there is a need to obtain the electrical resistance that is substantially the same or more of a copper wiring used at present, and to achieve this, the CNT must have its density of 1012 number/cm2 or more. In order to control the CNT density to be a desired high density, there is a need to form a catalytic material in fine particle state, which is to be nuclei for growing the CNTs, and to control a density and a size thereof. For example, Patent Document 1 discloses a technique in which after a catalytic metal layer is formed on an aluminum layer being a base thin film, fine particles including the catalytic metal are formed by heat treatment. Further, Non-Patent Document 1 discloses a technique in which catalytic fine particles previously generated by a laser ablation method are classified into desired sizes in a gaseous phase, and thereafter, they are deposited on a substrate in high density.
[Patent Document 1] Japanese Patent Application Laid-Open No. 2005-145743
[Patent Document 2] Japanese Patent Application Laid-Open No. 2003-277033
[Non-Patent Document 1] S. Sato et. al., CPL 382 (2003) 361
[Non-Patent Document 2] S. Sato et. al., in Proc. IEEE International Interconnect Technology Conference 2006, p. 230.
In order to generate the CNTs in high density, a densification of the catalytic fine particles is a must, and for that reason, it is required to control the sizes of the catalytic fine particles. In a method disclosed in Patent Document 1, it is difficult to control a shape of the catalytic fine particle, such as a diameter, and since the catalytic thin film is applied, the densification of the catalytic fine particles is difficult. Further, according to Non-Patent Document 1, it is possible to deposit the catalytic fine particles in high density by controlling the sizes thereof, but, an aggregation of each of the catalytic fine particles under a growth temperature is unavoidable, and even if the catalytic fine particles do not aggregate, when they contact with each other, an activity functioning as a catalyst of the CNT is lowered due to the contact, which prevents the densification of the CNTs.